Method and apparatus comprising a semiconductor device and test apparatus

ABSTRACT

A method of testing a semiconductor device. An apparatus comprising a semiconductor device and a test apparatus. The semiconductor device includes an integrated circuit and a plurality of external radiating elements at a surface of the device, the radiating elements include transmit elements and receive elements. The test apparatus includes a surface for placing against the surface of the device. The test apparatus also includes at least one waveguide, which extends through the test apparatus for routing electromagnetic radiation transmitted by one of the transmit elements of the device to one of the receive elements of the device. Each waveguide comprises a plurality of waveguide openings for coupling electromagnetically to corresponding radiating elements of the plurality of radiating elements located at the surface of the device. A spacing between the waveguide openings of each waveguide is larger than, or smaller than a spacing between the corresponding radiating elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority under 35 U.S.C. § 119 of EuropeanPatent application no. 20154940.9, filed on 31 Jan. 2020, the contentsof which are incorporated by reference herein.

BACKGROUND

The present specification relates to a method of testing a semiconductordevice and to an apparatus comprising a semiconductor device and a testapparatus.

Today's Radio Frequency (RF) transceiver Integrated Circuits (ICs) withintegrated radiating elements such as antennae or launchers requiretesting in production. This testing can include testing of the internaldie and testing of the antennae/launchers themselves, as well as theproperties of the package that can influence the performance of theantennae/launchers (such as the “artificial dielectric” which isrequired to achieve the required directional characteristic of theantennae/launchers).

Normally this test can only be done by an external loopback path fromtransmitter antennae/launchers to receiver antennae/launchers. Tightspecification parameters for IC transmit power, transmit and receiveantennae/launchers gain and receiver noise figure require this loopbackpath to be extremely precise, despite the very challenging environmentalconditions on production test floors.

In advanced radar transceiver ICs, a recently evolving technology is tointegrate transmit and receive antennae into the package (Antennae inPackage: AiP). Another technology is to integrate launchers into thepackage—these launchers are connected via wave guides to externalantennae of the package. For such ICs, RF transmitter output power andreceiver noise figure are key parameters, but measuring them isextremely difficult because the measurement result depends strongly on anumber of conditions such as:

-   -   the directivity characteristic of the integrated antennae;    -   impedance and matching of the integrated antennae to the on-chip        active device (e.g., Low Noise Amplifier (LNA), Power Amplifier        (PA));    -   the dielectric properties (e.g., δk and tan δ) of the stack-up        material used to realize the radiation directivity of the        integrated antennae;    -   x/y and z displacement of the integrated antennae with respect        to the reference antenna used for the measurement; and    -   the contact pressure of the measurement antenna to the IC        package.

These dependencies can be mitigated if the RF signals from the ICtransmit antennae are fed via an external loopback path to the ICreceive antennae, so that the IC can measure the received signalamplitude and phase.

The loopback path can be realized using a waveguide. The parameters ofthe waveguide such as wall thickness, surface roughness and alignmentaccuracy to the integrated antennae largely influence the measurements.Therefore, it is desirable to have a standardized loopback device to beused for all cases where RF parameters need to be precisely measuredincluding, for example:

-   -   validation at the IC manufacturer,    -   validation at the OEM manufacturer;    -   production test at the IC manufacturer,    -   customer reject analysis at the OEM;    -   customer reject analysis at the IC manufacturer;    -   qualification (e.g., life time tests) at the customer site; and    -   adjustment of new external antennae in the field, i.e. in car        workshops.

A solution for a standardized loopback device at the various sites,combining high precision, high sensitivity to antenna or launchermisalignments, but low sensitivity to misalignments of this loopbackdevice, is currently not available.

SUMMARY

Aspects of the present disclosure are set out in the accompanyingindependent and dependent claims. Combinations of features from thedependent claims may be combined with features of the independent claimsas appropriate and not merely as explicitly set out in the claims.

According to an aspect of the present disclosure, there is provided anapparatus comprising:

-   -   a semiconductor device comprising an integrated circuit and a        plurality of external radiating elements at a surface of the        device, the radiating elements including at least one transmit        element and at least one receive element; and    -   a test apparatus for testing the semiconductor device, the test        apparatus comprising:        -   a surface for placing against said surface of the device;            and        -   at least one waveguide, wherein each waveguide extends            through the test apparatus for routing electromagnetic            radiation transmitted by one of said transmit elements of            the device to one of the receive elements of the device,            wherein each waveguide comprises a plurality of waveguide            openings for coupling electromagnetically to corresponding            radiating elements of the plurality of radiating elements            located at the surface of the device,            wherein a spacing between the waveguide openings of each            waveguide of the test apparatus is larger than, or smaller            than a spacing between the corresponding radiating elements            of the device.

According to another aspect of the present disclosure, there is provideda method of testing a semiconductor device, the method comprising:

-   -   providing a semiconductor device comprising an integrated        circuit and a plurality of external radiating elements at a        surface of the device, the radiating elements including at least        one transmit element and at least one receive element:    -   providing a test apparatus for testing the semiconductor device,        the test apparatus comprising:        -   a surface for placing against said surface of the device;            and        -   at least one waveguide, wherein each waveguide extends            through the test apparatus for routing electromagnetic            radiation transmitted by one of said transmit elements of            the device to one of the receive elements of the device,            wherein each waveguide comprises a plurality of waveguide            openings for coupling electromagnetically to corresponding            radiating elements of the plurality of radiating elements            located at the surface of the device.    -   wherein a spacing between the waveguide openings of each        waveguide of the test apparatus is larger than, or smaller than        a spacing between the corresponding radiating elements of the        device, and    -   transmitting electromagnetic radiation from at least one said        transmit element to at least one said receive element via at        least one waveguide of the test apparatus.

By including a deliberate non-zero spacing mismatch between thewaveguide openings of each waveguide of the test apparatus and thecorresponding radiating elements of the device, sensitivity to furtherunintended mismatching between the waveguide openings and the radiatingelements (e.g. due to manufacturing variations or other sources) may bereduced.

The radiating elements of the semiconductor device may, for instance,comprise antennae and/or launchers. The transmit elements mayaccordingly, for instance, comprise transmit antennae or transmitlaunchers, while the receive elements may accordingly, for instance,comprise receive antennae or receive launchers.

A spacing between the waveguide openings of each waveguide of the testapparatus may be larger than, or smaller than, a spacing between thecorresponding radiating elements of the device by at least 0.1%. Aspacing between the waveguide openings of each waveguide of the testapparatus may be larger than, or smaller than, a spacing between thecorresponding radiating elements of the device by at least 1%.

In some embodiments, the spacing between the waveguide openings of eachwaveguide of the test apparatus may be smaller than the spacing betweenthe corresponding radiating elements of the device. In otherembodiments, the spacing between the waveguide openings of eachwaveguide of the test apparatus may be larger than the spacing betweenthe corresponding radiating elements of the device.

At least one of the waveguides may be configured to routeelectromagnetic radiation transmitted by one of said transmit elementsof the device to a plurality of receive elements of the device. This canallow the plurality of receive elements collectively to be used fortesting the transmit element (and vice versa), bearing in mind that thetransmit power of the transmit element may exceed the power receivableby a single receive element.

The apparatus waveguide may have:

-   -   a first branch for conveying electromagnetic radiation        transmitted by said transmit element; and    -   at least two further branches coupled to the first branch for        route said electromagnetic radiation to said plurality of        receive elements.

The semiconductor device may include a semiconductor die located in apackage. The surface of the device at which the plurality of externalradiating elements are located may be an external surface of thepackage.

The semiconductor device may include:

-   -   a semiconductor die located in a package; and    -   a carrier, wherein the package is mounted on a carrier,        wherein the surface of the device at which the plurality of        external radiating elements are located is a surface of the        carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of this disclosure will be described hereinafter, by way ofexample only, with reference to the accompanying drawings in which likereference signs relate to like elements and in which:

FIG. 1A shows a semiconductor device using strip line antennae;

FIG. 1B shows a semiconductor device using an external launcher;

FIG. 1C shows a semiconductor device using an integrated launcher;

FIGS. 2A, 2B and 2C illustrate a semiconductor device, dielectric layerand plunger according to an embodiment of this disclosure;

FIG. 3 shows a semiconductor device and dielectric layer according to anembodiment of this disclosure;

FIG. 4 show a semiconductor device and plunger according to anembodiment of this disclosure;

FIGS. 5A and 5B show a semiconductor device, dielectric layer andplunger according to an embodiment of this disclosure;

FIGS. 6A and 6B show a semiconductor device, dielectric layer andplunger according to an embodiment of this disclosure;

FIG. 7 shows a semiconductor device and plunger according to anembodiment of this disclosure;

FIG. 8 shows a semiconductor device and test apparatus according to anembodiment of this disclosure;

FIG. 9 shows the effect of mismatches between the lateral positions ofthe radiating elements of a semiconductor device and the waveguideopenings in a test apparatus; and

FIGS. 10 to 12 each show the effect of mismatches between the lateralpositions of the radiating elements of a semiconductor device and thewaveguide openings in a test apparatus according to an embodiment ofthis disclosure.

DETAILED DESCRIPTION

Embodiments of this disclosure are described in the following withreference to the accompanying drawings.

FIGS. 1A, 1B and IC each show an example of a semiconductor device 10.

The device 10 in FIG. 1A includes a semiconductor die 6 forms anintegrated circuit, which may typically include circuitry fortransmitting/receiving and processing mm-wave signals for use in, forexample, the automotive industry. The semiconductor die 6 may beencapsulated in an encapsulant 4. In this example, the semiconductor die6 is mounted on a surface of a carrier 2, such as a primed circuitboard. The carrier 2 may comprise, for example, RO3003 or RF4 materials.Electrical connections 8 between the carrier and the semiconductor die 6may be formed using, for example, an array of solder balls as shown inFIG. 1, although other kinds of connections of the kind known in the artmay be used also.

The semiconductor device 10 in each of FIGS. 1A, 1B and 1C includes aplurality of radiating elements located at a surface of the device 10.In the example of FIG. 1, the radiating elements are provided in theform of strip line antennae 12, 14 comprising metallic strips located onthe surface of the carrier 2. The radiating elements include a pluralityof transmit elements 12 and a plurality of receive elements 14.Electrical connections 16 between the radiating elements and thesemiconductor die 6 may be formed by a combination of metal trackslocated on the surface of the carrier 2 and the aforementionedelectrical connections 8.

The semiconductor device 10 shown in FIG. 1B is similar to that shown inFIG. 1A, except that the device 10 further includes a waveguide antenna20 which may be located on top of the semiconductor die 6 and thecarrier 2. The waveguide antenna 20 includes channels 18 for guidingelectromagnetic radiation to/from the plurality of receive elements 14and the plurality of transmit elements 12. These channels may terminatein an array of transmit elements 22 and an array of receive elements 24.In the example of FIG. 1B, it is the transmit elements 22 and thereceive elements 24 that form the radiating elements of thesemiconductor device 10. The arrangement of the strip line antennae andradiating elements in the example of FIG. 1B may be referred to as anexternal launcher.

The semiconductor device 10 shown in FIG. 1C is similar to that shown inFIG. 1C, except that the device 10 in FIG. 1C does not include stripline antennae as described above in relation to FIGS. 1A and 1B.Instead, the device 10 in FIG. 1C includes transmit elements 32 fortransmitting mm-wave signals and receive elements 34 for transmittingmm-wave signals which are provided inside the encapsulant 4. Electricalconnections 36 between the semiconductor die 6 and the transmit elements32 and receive elements 34 may pass through the encapsulant (and/or viathe electrical connections 8). Like the semiconductor device 10 of FIG.11, the semiconductor device 10 in FIG. 1C includes a waveguide antenna20, which may be located on top of the semiconductor die 6 and thecarrier 2. The waveguide antenna 20 includes channels 38 for guidingelectromagnetic radiation to/from the receive elements 34 and thetransmit elements 32. Again, these channels may terminate in an array oftransmit elements 22 and an array of receive elements 24. In the exampleof FIG. 1C, it is again the transmit elements 22 and the receiveelements 24 that form the radiating elements of the semiconductor device10. The arrangement of the transmit elements 32 and receive 34 andradiating elements 22, 24 in the example of FIG. 1C may be referred toas an integrated launcher.

In FIG. 1A, the encapsulant 4 may be considered to form a package of thesemiconductor die 6. In FIGS. 1B and 1C, the encapsulant 4 and/or thewaveguide antenna 20 may be considered to form a package of thesemiconductor die 6.

As noted previously, to test a semiconductor device 10 of the kind shownin FIGS. 1A-1C, it is necessary to test the operation of the radiatingelements. The test may involve placing a plunger against the surface ofthe semiconductor device 10, the plunger having waveguide openings forcoupling electromagnetically to the radiating elements of the device 10.The plunger may include a loopback path, allowing the receive elementsof the device 10 to receive electromagnetic radiation (mm-wave signals)transmitted by the transmit elements of the device 10. A solution for astandardized loopback path device at the various sites, combining highprecision, high sensitivity to radiating element misalignments, but lowsensitivity to misalignments of this loopback path device, is currentlynot available.

Test apparatuses according to embodiments of this disclosure will now bedescribed in relation to FIGS. 2 to 12.

FIG. 2A shows a semiconductor device 10 which shares features of thekind described above in relation to FIG. 1. The device 10 includes asemiconductor die 6 which may be provided in an encapsulant 30. Thedevice 10 also includes a waveguide antenna 20, which includes aplurality of radiating elements arranged in an array, which includestransmit elements 22 and receive elements 24 provided at a surface ofthe device 10. The semiconductor die 6, encapsulant 30 and waveguideantenna 20 may be mounted on a surface of a carrier 20, as explained inrelation to FIG. 1.

The test apparatus in this embodiment includes a dielectric portion 40,which may be included in a plunger. The dielectric portion 40 is shownin FIG. 2B with the remainder of the plunger omitted (further details ofthe plunger will be described below with reference to FIG. 2C. Thedielectric portion 40 may be provided in the form of a layer. Thedielectric portion 40 has a surface (the underside of the dielectricportion 40 shown in FIG. 2B), which may be placed against the surface ofthe semiconductor device 10 that includes the radiating elements of thedevice 10. The surface to be placed against the surface of thesemiconductor device 10 that includes the radiating elements of thedevice 10 may, for example, be substantially planar, although it alsomay in general be profiled to match the profile of the surface of thesemiconductor device 10. The dielectric portion 40 may also have asurface 42 (which is generally an opposite surface of the dielectricportion 40 to the surface which is to be placed against thesemiconductor device 10). Further features of the plunger (such as theplurality of waveguide openings of the plunger, to be described below)may be located against the surface 42 of the dielectric portion 40.

Turning to FIG. 2C, the plunger may further include a block 50, whichcan house a plurality of waveguide openings 60 and waveguides 52. Theblock may comprise a metal (e.g. copper). The waveguide openings 60 arearranged in locations that correspond to the locations of the transmitelements 22 and receive elements 24 provided at the surface of thedevice 10, thereby allowing the plurality of waveguide openings 60 tocouple electromagnetically to corresponding transmit/receive elements ofthe plurality of radiating elements located at the surface of thedevice.

The waveguides 52 may comprise channels that extend into the plungerfrom the waveguide openings 60, so as to route electromagnetic radiationtransmitted by the transmit elements 22 to the receive elements 24 in aloopback arrangement as explained previously. The waveguides may befilled with a dielectric. Each waveguide may extend between at least oneof the transmit elements 22 and at least one of the receive elements 24.As shown in FIG. 2C, the waveguide openings 60 may taper outwardly asthe extend away from the waveguides 52, so as to provide a bettermatching to the electromagnetic field in the dielectric portion 40.

The dielectric portion 40 is configured to provide a matched interfacefor the electromagnetic coupling of the plurality of waveguide openings60 of the plunger to the plurality of radiating elements (the transmitelements 22 and the receive elements 24) of the semiconductor device 10.To this end, the material of the dielectric portion 40 may be chosenaccording to the specific application and the electromagneticwavelengths to be used in the testing of the device 10. Suitablematerials for the dielectric portion 40 include high-densitypolyethylene (HDPE) and a polycarbonate such as Makrolon or Peek, or aceramic material. The thickness T (see FIG. 2B) of the dielectricportion 40 may also be chosen so as to enhance the matched interfacebetween the plurality of waveguide openings 60 of the plunger and theplurality of radiating elements (the transmit elements 22 and thereceive elements 24) of the semiconductor device 10. In particular, thethickness T of the dielectric portion 40 may be chosen to be λ/2, whereλ is a wavelength of the electromagnetic radiation to be used (i.e.transmitted by the transmit elements 22 and received by the receiveelements 24) during the testing of the semiconductor device 10. Notethat λ denotes the wavelength of the electromagnetic radiation insidethe dielectric portion 40. By way of example only, where the dielectricportion 40 comprises HDPE, and considering an example frequency of 77GHz, the thickness T may be chosen to be around 2.7 mm. In anotherexample, where the dielectric portion 40 comprises Makrolon, and againconsidering an example frequency of 77 GHz, the thickness T may bechosen to be around 2 mm.

The dielectric portion 40 may also act to provide a seal to preventunwanted airflow during testing of the semiconductor device 10 using thetest apparatus. For instance, by placing the dielectric portion 40against the surface of the semiconductor device 10 including theradiating elements of the device 10, the dielectric portion 40 may sealoff the surface of the semiconductor device 10 including the radiatingelements. This can prevent airflow around the radiating elements of thedevice 10, which may otherwise affect the results of the test. It isalso noted that the dielectric portion 40 may seal off the waveguideopenings 60 of the plunger, again to prevent unwanted airflow.

Although the embodiment of FIG. 2 is described in relation to asemiconductor device which, as described in FIGS. 1B and 1C, has awaveguide antenna 20, it is envisaged that the plunger may also be usedwith a semiconductor device 10 of the kind shown in FIG. 1A. In suchcases, the waveguide openings 60 of the plunger may couple directly withthe strip line antennae 12, 14 on the surface of the carrier 2, whichform the radiating elements of the device 10 in such embodiments.

In some embodiments, the dielectric portion may include a curvedsurface, for coupling electromagnetic radiation transmitted by aplurality of transmit elements 22 of the device 10 to a waveguideopening 60 of said plurality of waveguide openings of the plunger.Conversely, the curved surface may also allow coupling ofelectromagnetic radiation transmitted by one of the waveguide openings60 to a plurality of receive elements 24 of the device. An example ofsuch an embodiment is shown in FIG. 3. As with FIG. 2B, the dielectricportion 40 in FIG. 3 is shown with the remainder of the plunger omittedso as to reveal the configuration of the curved surface 44. The curvedsurface may act as a lens antenna. The curved surface 44 in thisembodiment is concave when viewed from the waveguide(s) of the plunger.In other embodiments, curved surface 44 may be convex when viewed fromthe waveguide(s) of the plunger. The curved surface 44 may, forinstance, have a substantially cylindrical profile as shown in FIG. 3,however other surface profiles are envisaged. The curvature of thecurved surface 44 may be chosen according to the dielectric constant ofthe material used to form the dielectric portion 40. The space createdbetween the curved surface 44 and the waveguide openings 60 of theplunger may be filled with another dielectric, such as air.

In some embodiments, at least one of the waveguides of the plunger maybe configured to route electromagnetic radiation transmitted by one ofthe transmit elements 22 of the device 10 to a plurality of receiveelements 24 of the device 10. Examples of this will be described belowin relation to the embodiments of FIGS. 4 and 5.

FIG. 4 schematically illustrates the coupling of a plurality ofwaveguide openings 60 of a plunger according to an embodiment of thisdisclosure to a plurality of transmit elements 22 (Tx1, Tx2, Tx3) and aplurality of receive elements 24 (Rx1, Rx2, Rx3, Rx4) of a semiconductordevice 10. In this embodiment, waveguide 62 of the plunger routeselectromagnetic radiation from transmit element Tx1 to receive elementRx4, while waveguide 66 routes electromagnetic radiation from transmitelement Tx2 to receive element Rx3. Accordingly, waveguides 62, 66 eachroute electromagnetic radiation between a single transmit element 22 anda single receive element 24. However, as can be seen in FIG. 4,waveguide 64 in this embodiment routes electromagnetic radiation fromtransmit element Tx3 to receive element Rx1 and also to receive elementRx2. This kind of arrangement can allow a plurality of receive elements24 collectively to be used for testing the transmit element 22 (and viceversa) of the device 10, bearing in mind that the transmit power of thetransmit element 22 may exceed the power receivable by a single receiveelement 24.

In order to implement the routing of electromagnetic radiation from atransmit element 22 of the device 10 to more than one receive element 24of the device 10, the waveguide used (e.g. see waveguide 64 in FIG. 4)may include a plurality of branches. In FIG. 4 for instance, thewaveguide 64 in FIG. 4 includes a first branch 64A for conveyingelectromagnetic radiation transmitted by transmit element Tx1, a secondbranch 64B for routing the electromagnetic radiation to receive elementRx1 and a third branch 64C for routing the electromagnetic radiation toreceive element Rx2. The first branch 64A of waveguide 64 in thisembodiment thus splits into two separate branches 64B, 64C at location65.

FIGS. 5A and 5B show an example construction of a plunger having atleast one branched waveguide of the kind described above in relation toFIG. 4. FIG. 5A is a 3D view, while FIG. 5B is a plan view, viewed fromabove the surface to the semiconductor device 10 having the radiatingelements. The semiconductor device 10 itself is also shown in FIG. 5A.

The arrangement of the waveguides 62, 64, 66 in FIGS. 5A and 5B issimilar to that shown in FIG. 4, with the waveguides 62, 66 each routingelectromagnetic radiation between a single transmit element 22 and asingle receive element 24 and the waveguide 64 including multiplebranches for routing of electromagnetic radiation from a transmitelement 22 of the device 10 to more than one receive element 24 of thedevice 10. FIGS. 5A and 5B also include a cut out 70 in the block 50,which may be receiving a nozzle of the plunger, for use in moving theplunger into position during the test procedure. As can be seen in FIGS.5A and 5B, the waveguides 62, 64, 66 can be shaped around the cut out70—for instance the branches of the waveguide 64 split on one side ofthe cut out, and the branches leading to the receive elements 24 of thedevice 10 may extend through the plunger on opposite sides of the cutout 70.

FIGS. 6A and 6B show an example construction of a plunger having atleast one branched waveguide of the kind described above in relation toFIG. 4. FIG. 6A is a cross section, while FIG. 6B is a plan view, viewedfrom above the surface to the semiconductor device 10 having theradiating elements. The semiconductor device 10 itself is also shown inFIG. 6A.

The arrangement of the waveguides 62, 64, 66 in FIGS. 6A and 6B is againsimilar to that shown in FIG. 4, with the waveguides 62, 66 each routingelectromagnetic radiation between a single transmit element 22 and asingle receive element 24 and the waveguide 64 including multiplebranches for routing of electromagnetic radiation from a transmitelement 22 of the device 10 to more than one receive element 24 of thedevice 10.

In this embodiment, the routing of the waveguides is implemented using aprinted circuit board (PCB) 100 located on the plunger. The PCB 100includes patterned metal features 102 that are shaped and configured soas to route the electromagnetic radiation in the waveguides. It isenvisaged that a PCB 100 of the kind described here in relation to FIGS.6A and 6B may also be used to implement routing in a plunger that doesnot include branched waveguides such as waveguide 64, but in which eachwaveguide routes the electromagnetic radiation from a single transmitelement 22 to a single receive elements 24 of the device 10.

In some embodiments one or more of the waveguides may be provided withan attenuating portion for attenuating the electromagnetic radiationtransmitted by the transmit element/elements 22 of the semiconductordevice 10 before it is looped back around to the receiveelement/elements 24 of the device 10. An example of this is shown in theembodiment of FIG. 7. As shown in FIG. 7, the attenuating portion 90 maybe located inside waveguide 68. Suitable materials for the attenuatingportion include an absorbing foam such a those available from ECOSORB.The attenuating portion 90 can allow a receive element 24 of thesemiconductor device 10 to receive electromagnetic radiation from one(or more) transmit elements 22 of the semiconductor device 10, bearingin mind that the transmit power of the transmit element/elements 22 mayexceed the power receivable by a single receive element 24.

In a standard way of measuring the RF parameters of a mmWave device, theRF parameters of a mmWave integrated circuit are directly measuredduring validation, production testing, at the customer validation site,and in repair workshops in the field. This generally requires mmWavetest lab equipment, standardized measurement antennae and severalmeasurement parameters to be standardized. Despite the high effort andcosts for such measurements, the result is often too imprecise and notsufficiently repeatable and reproducible. Accordingly, this proceduredoes not fit for precise mmWave radar measurements in varyingenvironments, with varying measurement equipment and several otherparameters, which are hard to standardize.

As explained previously, testing of a mmWave device can be performed byforming a loopback path, in which the electromagnetic radiationtransmitted by transmit elements of a device may be looped back to thereceive elements of the device. Testing of this kind may involve thefollowing steps.

First, the RF parameters on several integrated circuits may be directlymeasured in a nmWave RF lab. Then, the RF parameters of these integratedcircuits may be determined using an external device containing aloopback path. The RF lab can correlate the RF parameters, measured bythe lab equipment, with the RF loopback parameters as measured by theloopback method. The RF loopback parameters, measured under standardizedconditions, can then then serve as a reference.

Accordingly, following this approach, what is guaranteed to thecustomers are the parameters measured by loopback test using astandardized loopback device, not those parameter measured in a mmWaveRF lab. In other words, what is guaranteed to the customers is thereceive power, and the receive noise level, measured by the integratedcircuit when the loopback device is used. What is not guaranteed istransmitter output power or the receiver noise figure.

The loopback device may then be used in all occurrences the RFparameters are needed, for instance in validation, production testing,testing of customer rejects, testing at the customer site and in carrepair workshops.

FIG. 8 schematically illustrates the test setup for testing asemiconductor device of the kind described here, using the loopbackapproach. The setup includes the test apparatus 100, which may includewaveguides having waveguide openings 60 for looping the electromagneticradiation transmitted by the transmit elements 22 of the device 10 undertest to the receive elements 24 of the device 10. For simplicity, thedevice 10 illustrated in FIG. 8 includes a single transmit element 22and a single receive element, while the test apparatus includes tworespective waveguide openings 60 and a single, non-branched, waveguide.Nevertheless, it will be appreciated that the principles to be describedbelow apply also to devices 10 including more than one transmit element22 and/or receive element 24 and to test apparatuses includingcorresponding waveguide openings 60, as well as to test apparatusesincluding branched waveguides as explained in relation to FIGS. 4 and 5.

A potential issue with a test setup of the kind shown in FIG. 8 is thatmisalignment of the waveguide openings 60 of the test apparatus 100 withthe radiating elements 22, 24 of the device 10 under test can lead toinaccurate test results. In FIG. 8, a lateral misalignment between thetransmit element 22 of the device 10 and the corresponding waveguideopening 60 of the test apparatus 100 is denoted as Δx_(tx), while amisalignment between the receive element 22 of the device 10 and thecorresponding waveguide opening 60 of the test apparatus 100 is denotedas Δx_(rx).

FIG. 9 illustrates the effects of the misalignments noted above. Thevertical axis in FIG. 9 denotes the coupling factor (in dB) between thetransmit element 22 of the device 10 and the corresponding waveguideopening 60 of the test apparatus 100 (left hand curve) and the couplingfactor between the receive element 24 of the device 10 and thecorresponding waveguide opening 60 of the test apparatus 100 (right handcurve). The coupling factor is shown as a function of misalignmentΔx_(tx) (left hand curve) and misalignment Δx_(rx) (right hand curve).Note that for each radiating element 22, 24, it is assumed the peakcoupling factor occurs when Δx_(tx) and Δx_(rx) are zero, i.e. when eachradiating element 22, 24 and its corresponding waveguide opening 60 arepositioned directly opposite each other, without any lateralmisalignment (represented by Tx1 and Rx1 in FIG. 9). As can be seen fromthe curves in FIG. 9, the coupling factor decreases with increasingpositive or negative misalignment Δx_(tx), Δx_(rx).

It will be appreciated that, assuming the fixed lateral spacing betweenthe transmit element 22 and the receive element 24 is equal to the fixedlateral distance between the corresponding waveguide opening 60 of thetest apparatus 100, a lateral misalignment between transmit element 22and its corresponding waveguide opening 60 of the test apparatus 100results in a corresponding lateral misalignment between receive element24 and it corresponding waveguide opening 60 of the test apparatus 100.That is to say, in FIG. 9, in general Δx_(tx)=Δx_(rx).

Tx2 and Rx2 in FIG. 9 correspond to a small misalignment, while Tx3 andRx3 correspond to a larger misalignment. The coupling factor for eachradiating element/waveguide opening pair at Tx2, Rx2 is reduced comparedto Tx1, Rx1 (Δx_(tx)=Δx_(rx)=0) owing to the small misalignment of theradiating elements/waveguide openings, while the coupling factor foreach radiating element/waveguide opening pair at Tx3, Rx3 is furtherreduced compared to Tx2, Rx2 owing to the larger misalignment of theradiating elements/waveguide openings.

In accordance with embodiments of this disclosure, the lateral spacingbetween the waveguide openings 60 of the test apparatus 100 isintentionally made larger than, or smaller than the lateral spacingbetween the corresponding transmit elements 22 and receive elements 24of the device 10. As will now be explained in relation to FIG. 10, thisautomatically (and counterintuitively) leads to misalignments betweenthe transmit and receive elements 22, 24 of the device 10 under test andthe corresponding waveguide openings 60 of the test apparatus 100.

Like FIG. 9, FIG. 10 shows the coupling factor between the transmitelement 22 of a device 10 under test and its corresponding waveguideopening 60 of the test apparatus 100 (left hand curve), and the couplingfactor between the receive element 24 of a device 10 under test and itscorresponding waveguide opening 60 of the test apparatus 100 (right handcurve). In this embodiment, the lateral spacing between the waveguideopenings 60 of the test apparatus 100 is intentionally smaller than thelateral spacing between the transmit and receive elements 22, 24. Whenthe test apparatus 100 is moved into its measurement position, therewill therefore always be at least some misalignment between either thetransmit element 22 and its corresponding waveguide opening 60 and/orthe receive element 24 and its corresponding waveguide opening 60.

In FIG. 10, three example positions of the test apparatus 100 areillustrated: Tx1, Rx1; Tx2, Rx2; and Tx3, Rx3.

Note that position Tx2, Rx2 gives rise to an equal amount ofmisalignment (although in the opposite direction) between the transmitelement 22 and its corresponding waveguide opening 60 of the testapparatus 100 and between the receive element 24 and its correspondingwaveguide opening 60. That is to say that for position Tx2, Rx2,(Δx_(tx)=−Δx_(rx)).

At position Tx1, Rx1, the misalignment between the transmit element 22and its corresponding waveguide opening 60 is reduced relative toposition Tx2, Rx2, whereas the misalignment between the receive element24 and its corresponding waveguide opening 60 is increased. Similarly,at position Tx3, Rx3, the misalignment between the transmit element 22and its corresponding waveguide opening 60 is increased relative toposition Tx2, Rx2, whereas the misalignment between the receive element24 and its corresponding waveguide opening 60 is reduced. Accordingly,it will be appreciated that there is a tendency for reductions in theoverall coupling factor resulting from misalignments relative toposition Tx2, Rx2 to cancel out (bearing in mind that the loopback testarrangement requires the electromagnetic radiation passing through thewaveguide of the test apparatus 100 to be coupled twice between thedevice 10 and the test apparatus 100: once at the transmit element 22and once at the receive element 24). Because of this, the aforementionedintentional reduction in the lateral spacing between the waveguideopenings 60 of the test apparatus 100 has led to an overall reduction insensitivity of coupling factor to misalignments (relative to positionTx2, Rx2) between the waveguide openings 60 of the test apparatus 100and those of the device 10 under test. To a first order approximation,the overall coupling factors Tx1+Rx1≈Tx2-Rx2≈Tx3+Rx3. This can improvethe accuracy and repeatability of tests on semiconductor devices 10 ofthe kind described herein, using a test apparatus 100 having a loop backwaveguide arrangement.

It will be appreciated, for example with reference to FIG. 11, thatalthough in the embodiment of FIG. 10 the lateral spacing between thewaveguide openings 60 is smaller than the lateral spacing between thetransmit and receive elements 22, 24, similar benefits can arise incases in which the lateral spacing between the waveguide opening 60 islarger than the lateral spacing between the transmit and receiveelements 22, 24. In FIG. 11, three example positions of the testapparatus 100 are again illustrated, although this time for a testapparatus 100 in which the lateral spacing between the waveguideopenings 60 is larger than the lateral spacing between the transmit andreceive elements 22, 24: Tx1, Rx1; Tx2, Rx2; and Tx3, Rx3.

Again position Tx2, Rx2 gives rise to an equal amount of misalignment(although in the opposite direction) between the transmit element 22 andits corresponding waveguide opening 60 of the test apparatus 100 andbetween the receive element 24 and its corresponding waveguide opening60. That is to say that for position Tx2, Rx2, (−Δx_(tx)=Δx_(rx)).

In FIG. 11, at position Tx1, Rx1, the misalignment between the transmitelement 22 and its corresponding waveguide opening 60 is again reducedrelative to position Tx2, Rx2, whereas the misalignment between thereceive element 24 and its corresponding waveguide opening 60 is againincreased. Similarly, at position Tx3, Rx3, the misalignment between thetransmit element 22 and its corresponding waveguide opening 60 is againincreased relative to position Tx2, Rx2, whereas the misalignmentbetween the receive element 24 and its corresponding waveguide opening60 is again reduced. Accordingly, it will again be appreciated thatthere is a tendency for reductions in the overall coupling factorresulting from misalignments relative to position Tx2, Rx2 to cancelout. Because of this, the aforementioned intentional increase in thelateral spacing between the waveguide openings 60 of the test apparatus100 has led to an overall reduction in sensitivity of coupling factor tomisalignments (relative to position Tx2, Rx2) between the waveguideopenings 60 of the test apparatus 100 and those of the device 10 undertest. Again, to a first order approximation, the overall couplingfactors Tx1+Rx1≈Tx2-Rx2≈Tx3+Rx3. As with the embodiment of FIG. 10, thiscan therefore improve the accuracy and repeatability of tests onsemiconductor devices 10 of the kind described herein, using a testapparatus 100 having a loop back waveguide arrangement.

The lateral spacing between the waveguide openings 60 of the testapparatus 100 may differ from (i.e. larger than or smaller than) thelateral spacing between the transmit and receive elements 22, 24 by anamount that may, for instance, be chosen according to the shape (e.g.slope, width etc.) of the coupling factor curves. Typically it isenvisaged that the spacing between the waveguide openings 60 of the testapparatus 100 may larger than, or smaller, than the spacing between thecorresponding transmit and receive elements 22, 24 of the device 10 byat least 0.1%, or by at least 1%.

According to embodiments of this disclosure, intentional smaller orlarger lateral spacing between the waveguide openings may be employed inany test apparatus having:

-   -   a test apparatus for testing the semiconductor device, the test        apparatus comprising:        -   a surface for placing against the surface of the device; and        -   at least one waveguide, wherein each waveguide extends            through the test apparatus for routing electromagnetic            radiation transmitted by one of said transmit elements of            the device to one of the receive elements of the device,            wherein each waveguide comprises a plurality of waveguide            openings for coupling electromagnetically to corresponding            radiating elements of the plurality of radiating elements            located at the surface of the device.

The test apparatus may, for instance, include a test apparatus of thekind described above in relation to any of FIGS. 1 to 7, although it isenvisaged that the previously described dielectric portion 40 may, ormay not be present in such embodiments.

The semiconductor device under test may comprise an integrated circuitand a plurality of external radiating elements located at a surface ofthe device, the external radiating elements including at least onetransmit element and at least one receive element. By way of example,the device under test may be a device 10 of the kind described above inrelation to any of FIGS. 1 to 7.

Testing of a semiconductor device 10 comprising an antenna in package(AiP) or Launcher in Package (LiP) such as those described in relationto FIG. 1 may generally not simply involve testing the radiatingelements of the device 10. The testing may also involve testing anyinternal antenna of the device 10 (for instance the strip line antennae12, 14 shown in FIG. 1B or the transmit and receive elements 32, 34shown in FIG. 1C). The testing may also involve the so-called“artificial dielectric”—this are structures which make sure that thetransmit and receive elements have the intended directionalcharacteristics.

Temperature cycling, aging and/or production variations/defects may leadto defects which manifest in different ways. In some cases, the positionof one of the transmit or receive elements of the device 10 may beshifted to a different position to that intended during manufacture. Inmore frequent cases, the geometrical antenna position may stay the same,but the apparent antenna position (i.e. the effective position accordingto the antenna directivity) may change. This can lead to the RFproperties (e.g. gain, directivity) of the antennae of the devicechanging, as though the position of the antennae had changed, eventhough the actual positions of the antennae may remain unchanged. It isdesirable that these effects are also accounted for during the loop backtest procedure. Although it is desirable that these measurements beinsensitive to misalignments of the test apparatus, it is also desiredthat they be sensitive to any changes (real or apparent) of the antennaethemselves.

FIG. 12 shows the coupling factor between the transmit element 22 of adevice 10 under test and its corresponding waveguide opening 60 in thetest apparatus 100, and the coupling factor between the receive element24 of the device 10 and its corresponding waveguide opening 60 in thetest apparatus 100. In FIG. 12 it is assumed that the lateral spacingbetween the waveguide openings 60 in the test apparatus 100 is smallerthan the lateral spacing between the transmit element 22 and the receiveelement 24 as described above in relation to FIG. 10.

In FIG. 12, position Tx, Rx2 is considered to be the “nominal” position,and corresponds to the position Tx2, Rx2 in FIG. 10. FIG. 12 also showstwo example deviations from Tx, Rx2, namely Tx, Rx1 and Tx, Rx3. Tx, Rx1and Tx, Rx3 each correspond to a change in lateral spacing (real orapparent) between the transmit and receive elements 22, 24 of thesemiconductor device 10. In particular, in the case of Tx, Rx1, thelateral spacing between the transmit and receive elements 22, 24 isincreased, whereas in the case of Tx, Rx3, the lateral spacing betweenthe transmit and receive elements 22, 24 is decreased.

As can be seen, compared to Tx2, Rx2, a slight increase of the distance(Tx, Rx3) leads to worse coupling at the receive element 24. Likewise, aslight decrease of the distance (Tx, Rx1) leads to better coupling atthe receive element 24. Hence, the change of the overall loopbacktransmission factor, Tx+Rx1, Tx+Rx3 versus the standard case Tx+Rx2, islarge in this example (Tx+Rx1>>Tx+Rx2; Tx+Rx3<<Tx+Rx2). Accordingly, itwill be appreciated that the sensitivity of the test procedure tovariations in the lateral spacing in the radiating elements of thedevice 10 under test is generally large, notwithstanding the fact thatthe lateral spacing between the waveguide openings of the test apparatus100 is intentionally different to the “nominal” spacing represented byTx, Rx2. Although FIG. 12 has been explained under the assumption thatthe lateral spacing of the waveguide openings 60 is intentionallysmaller than the lateral spacing of the transmit and receive elements22, 24 of the device 10 under test (as per FIG. 10), it will beappreciated that the sensitivity of the test procedure to variations inthe lateral spacing in the radiating elements of the device 10 undertest will also generally be large for lateral spacings of the waveguideopenings 60 that are intentionally larger than the lateral spacing ofthe transmit and receive elements 22, 24 of the device 10 under test (asper FIG. 11).

Accordingly, there has been described a method of testing asemiconductor device. An apparatus comprising a semiconductor device anda test apparatus. The semiconductor device includes an integratedcircuit and a plurality of external radiating elements at a surface ofthe device, the radiating elements include transmit elements and receiveelements. The test apparatus includes a surface for placing against thesurface of the device. The test apparatus also includes at least onewaveguide, which extends through the test apparatus for routingelectromagnetic radiation transmitted by one of the transmit elements ofthe device to one of the receive elements of the device. Each waveguidecomprises a plurality of waveguide openings for couplingelectromagnetically to corresponding radiating elements of the pluralityof radiating elements located at the surface of the device. A spacingbetween the waveguide openings of each waveguide is larger than, orsmaller than a spacing between the corresponding radiating elements.

Although particular embodiments of this disclosure have been described,it will be appreciated that many modifications/additions and/orsubstitutions may be made within the scope of the claims.

What is claimed is:
 1. An apparatus comprising: a semiconductor devicecomprising an integrated circuit and a plurality of external radiatingelements at a surface of the semiconductor device, the radiatingelements including at least one transmit element and at least onereceive element; and a test apparatus for testing the semiconductordevice, the test apparatus comprising: a surface for placing againstsaid surface of the semiconductor device; and at least one waveguide,wherein each waveguide extends through the test apparatus for routingelectromagnetic radiation transmitted by one of said transmit elementsof the semiconductor device to one of the receive elements of thesemiconductor device, wherein each waveguide comprises a plurality ofwaveguide openings for coupling electromagnetically to correspondingradiating elements of the plurality of radiating elements located at thesurface of the semiconductor device, wherein a spacing between thewaveguide openings of each waveguide of the test apparatus is largerthan, or smaller than a spacing between the corresponding radiatingelements of the semiconductor device, and wherein at least one of thewaveguides is configured to route electromagnetic radiation transmittedby one of said transmit elements of the semiconductor device to aplurality of receive elements of the semiconductor device, wherein saidwaveguide comprises: a first branch for conveying electromagneticradiation transmitted by said transmit element; and at least two furtherbranches coupled to the first branch for routing said electromagneticradiation to said plurality of receive elements.
 2. The apparatus ofclaim 1, wherein a spacing between the waveguide openings of eachwaveguide of the test apparatus is larger than, or smaller, than aspacing between the corresponding radiating elements of thesemiconductor device by at least 0.1%.
 3. The apparatus of claim 2,wherein a spacing between the waveguide openings of each waveguide ofthe test apparatus is larger than, or smaller than, a spacing betweenthe corresponding radiating elements of the semiconductor device by atleast 1%.
 4. The apparatus of claim 1, wherein the spacing between thewaveguide openings of each waveguide of the test apparatus is smallerthan the spacing between the corresponding radiating elements of thesemiconductor device.
 5. The apparatus of claim 1, wherein the spacingbetween the waveguide openings of each waveguide of the test apparatusis larger than the spacing between the corresponding radiating elementsof the semiconductor device.
 6. The apparatus of claim 1, wherein thesemiconductor device comprises a semiconductor die located in a package,and wherein the surface of the semiconductor device at which theplurality of external radiating elements are located is an externalsurface of the package.
 7. The apparatus of claim 1, wherein thesemiconductor device comprises: a semiconductor die located in apackage; and a carrier, wherein the package is mounted on a carrier,wherein the surface of the semiconductor device at which the pluralityof external radiating elements are located is a surface of the carrier.8. The apparatus of claim 1, wherein the test apparatus furthercomprises a dielectric portion forming said surface for placing againstsaid surface of the semiconductor device, wherein the dielectric portionis configured to provide a matched interface for said electromagneticcoupling of the plurality of waveguide openings to the plurality ofradiating elements of the semiconductor device.
 9. The apparatus ofclaim 8, wherein the dielectric portion has a thickness, measuredbetween the plurality of radiating elements located at a surface of thesemiconductor device and the plurality of waveguide openings, which issubstantially equal to λ/2, where λ is a wavelength of saidelectromagnetic radiation in the dielectric portion.
 10. The apparatusof claim 8, wherein the dielectric portion comprises a curved surfacefor coupling electromagnetic radiation transmitted by a plurality oftransmit elements of the semiconductor device to an opening of saidplurality of waveguide openings.
 11. The apparatus of claim 1, furthercomprising an attenuating portion located in at least one of saidwaveguides.
 12. A method of testing a semiconductor device, the methodcomprising: providing a semiconductor device comprising an integratedcircuit and a plurality of external radiating elements at a surface ofthe semiconductor device, the radiating elements including at least onetransmit element and at least one receive element; providing a testapparatus for testing the semiconductor device, the test apparatuscomprising: a surface for placing against said surface of thesemiconductor device; and at least one waveguide, wherein each waveguideextends through the test apparatus for routing electromagnetic radiationtransmitted by one of said transmit elements of the semiconductor deviceto one of the receive elements of the semiconductor device, wherein eachwaveguide comprises a plurality of waveguide openings for couplingelectromagnetically to corresponding radiating elements of the pluralityof radiating elements located at the surface of the semiconductordevice, wherein a spacing between the waveguide openings of eachwaveguide of the test apparatus is larger than, or smaller than aspacing between the corresponding radiating elements of thesemiconductor device, and transmitting electromagnetic radiation from atleast one said transmit element to a plurality of said receive elementsvia at least one waveguide of the test apparatus, the at least onewaveguide comprising a first branch for conveying electromagneticradiation transmitted by said transmit element and at least two furtherbranches coupled to the first branch for routing said electromagneticradiation to said plurality of receive elements.
 13. The method of claim12, wherein a spacing between the waveguide openings of each waveguideof the test apparatus is larger than, or smaller than, a spacing betweenthe corresponding radiating elements of the semiconductor device by atleast 0.1%.
 14. The method of claim 13, wherein a spacing between thewaveguide openings of each waveguide of the test apparatus is largerthan, or smaller than, a spacing between the corresponding radiatingelements of the semiconductor device by at least 1%.
 15. The method ofclaim 12, wherein the spacing between the waveguide openings of eachwaveguide of the test apparatus is smaller than the spacing between thecorresponding radiating elements of the semiconductor device.
 16. Themethod of claim 12, wherein the spacing between the waveguide openingsof each waveguide of the test apparatus is larger than the spacingbetween the corresponding radiating elements of the semiconductordevice.
 17. The method of claim 12, wherein said transmittingelectromagnetic radiation from at least one said transmit element to atleast one said receive element via at least one waveguide of the testapparatus comprises at least one of the waveguides routingelectromagnetic radiation transmitted by one of said transmit elementsof the semiconductor device to a plurality of receive elements of thesemiconductor device.
 18. The method of claim 12, wherein the testapparatus further comprises a dielectric portion forming said surfacefor placing against said surface of the semiconductor device, whereinthe dielectric portion provides a matched interface for saidelectromagnetic coupling of the plurality of waveguide openings to theplurality of radiating elements of the semiconductor device.